Human dermis is a layer of skin between the epidermis and subcutaneous tissue. The epidermis, serves as a barrier to protect the body against microbial pathogens, oxidant stress (UV light), water loss and chemical compounds, and provides mechanical resistance. The subcutaneous tissue consists of connective tissue and functions as a cushion for the body from stress and strain. The dermis is tightly connected to the epidermis through a basement membrane. Structural components of the dermis are collagen, elastic fibers, glycosaminoglycan, and extra fibrillar matrix. The glycosaminoglycan, e.g. hyaluronan, has multiple functions such as, to ensure good hydration, to assist in the organization of the extracellular matrix (ECM), to act as a filler material, and to participate in tissue repair mechanisms. The extracellular matrix plays an important role in skin aging: in young skin, the collagen fibers form a three-dimensional network. The fibroblasts bind to collagen fibrils via multiple contact sites (integrins) on their surface. This binding builds up a tensile stress, which balances the synthesis of collagen and collagen-degrading matrix-metalloproteins in the fibroblasts. In aged skin, the structure of the extracellular matrix is damaged by collagen breakdown—partial fragmentation of the collagen.
Skin aging is a progressive phenomenon, occurs over time and can be affected by lifestyle factors, such as alcohol consumption, tobacco and sun exposure. Aging of the facial skin can be characterized by atrophy, slackening, and fattening. Atrophy corresponds to a massive reduction of the thickness of skin tissue. Slackening of the subcutaneous tissues leads to an excess of skin and ptosis and leads to the appearance of drooping cheeks and eye lids. Fattening refers to an increase in excess weight by swelling of the bottom of the face and neck. These changes are typically associated with dryness, loss of elasticity, and rough texture.
To improve cell function of skin, there are two main approaches: one is to supply skin cells with essential building blocks through oral nutrition and supplements or topical creams and serums or vigorous daily exercise to increase blood-flow and encourage the lymphatic system; the other approach relates to optimizing release of growth factors, i.e. substances that cause cells to differentiate, proliferate and/or grow, and cytokines which signal molecules released by cells to communicate with other cells. However, applying active ingredients topically to skin in order to improve cell function has generally not been highly effective, likely due to the impermeable nature of stratum corneum and other superficial layers of the epidermis.
Non-invasive or low-invasive techniques and devices for facilitating delivery of beneficial agents into skin have been proposed. For example, microneedle devices have been used to create numerous shallow punctures in the dermis, with the goal of enabling better penetration of topical compositions into the punctured skin. Such microneedle devices are used to perforate the skin and topical compositions are then sometimes applied to the punctured skin.
There remains an unmet need for better methods, devices and treatments for improving skin conditions, for example, in order to optimize skin health and improve outward appearance.